LAMELLIBRANCHIA TA. 
403 
SpHENOTUS FLAVIUS. 
PLATE LXVI, FIGS. 27-29. 
Sanguinolites ? flavins, Hall. Prelim. Notice Lamellibranchiata, 2, p. 47. 1S70. 
“ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 66, figs. 27-29. 1883. 
Shell of medium size, elongate, sub-cylindrical; length nearly three times the 
height in the vertically compressed specimen described; basal margin gently 
curving, straight or slightly constricted about the middle of its length. Pos¬ 
terior extremity narrowly rounded or sub-acute, obliquely truncate above. 
Cardinal line straight, nearly parallel to the basal margin. Anterior end 
short, narrowly and sub-acutely rounded. 
Valves moderately convex below and posteriorly, gibbous in the middle 
and umbonal region. 
Beaks sub-anterior, moderately prominent. Umbonal slope rounded, 
scarcely sub-angular near the beaks, extending to the posterior extremity. 
Post-cardinal slope with an obscure fold or plication. Cincture oblique, not 
strongly defined, extending from the beaks to near the middle of the base. 
Surface marked by fine concentric strice of growth, which become fascicu¬ 
late and form unequal undulations upon the posterior and umbonal portions 
of the shell; also marked by fine radiating strice. Interior unknown. 
The specimen described has a length of 44 mm. and a height of 14.5 mm. 
This species differs from any of the preceding forms in the anterior position 
of the beaks. The extension of the umbonal slope to the middle of the poste¬ 
rior end, and the gaping of the valves, are due to vertical compression. 
Formation and locality. In the Waverly sandstones of Licking county, 0. 
Spiienotus valvulus. 
PLATE LXVI, FIG. 30. 
*S 'anguinolites volvulus, Hall. Prelim. Notice Lamellibranchiata, 2, p. 46. 1870. 
“ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PL 66, fig. 30. 1883. 
Shell large, sub-cylindrical, very elongate posteriorly; length less than three 
times the height; basal margin very gently curving, with a slight constric- 
